Directional sound-detecting device



Dec. 29 1925- W. D. COOLIDGE DIRECTIONAL SOUND DETECTING DEVICE Filed 001:. 8. 1918 Wi Hiam D. Coolid Hns Afifotney.

Patented Dec. 29, 1925.

UNITED STATES PATENT OFFICE.

WILLIAM D. COOLIDGE, OFSCHENEGTADY, NEW YORK, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK.

. DIRECTIONAL SOUND-DETECTING DEVICE.

Application filed October 8, 1918. Serial No. 257,361.

To all whom it may concern:

Be it known that I, WILLIAM D. CooLmeE,

a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Directional Sound- Detecting Devices, of which the following is a specification.

My present invention relates to means for detecting and locating sounds, and more especially sounds transmitted through a fluid medium such as water.

In carrying out my invention in actual practice the sound waves are received by a diaphragm of soft rubber which is thereby set into corresponding vibration. This rubber diaphragm may take a variety of forms, some of which are tubular or hollow and of sufficient thickness to resist the hydrostatic pressure when the device is deeply immersed in water. I have found that soft rubber, purePara-rubber, especially, is peculiarly adapted as a diaphragm for reproducing sound vibrations in water with great faithfulness and accuracy, that is to say, with only very slight resonance effects, which would tend'to magnify some components of the sound more than others. In furtherance of this end it is desirable that the rubber 30 receiving diaphragm should be so arranged as to be unstretched and thus substantially free from stress or strain except such as may be due to the pressure effect of the water in which the diaphragm is'immersed while in use. The sound waves produced by vibration of the rubber diaphragm may be transmitted through an open tube to a stethoscope, ear-piece or receiver and thus rendered perceptible to the observer.

A further embodiment of my invention comprises the application of a plurality of sound receiving devices of the general nature indicated, for determining the direction of an object from which a sound is proceeding. This arrangement has been found highly useful for detecting the direction of submarine noises such as those emanating from signal stations, submarine boats and the like.

The various features of novelty which characterize my invention will be pointed out with particularity in the appended claims,

but the invention itself, however, as to its.

details of construction and arrangement of parts, will be better understood by reference to the following description taken in connection with the accompanying drawings in which- Fig. 1 represents one embodiment of a directional sound detecting device made in accordance with my invention;

Fig. 2 is a modification of a part thereof;

And Figs. 3, 4 and 5 are details of parts.

Fig. 4 shows in sectional view at 1 a thick walled soft rubber tube, the end of which has been closed at 2 by being pressed and cemented together and vulcanized with the ends thus closed, whereby a tight closure results. In one form or size which I have found convenient and successful this tube may be in the neighborhood of six inches long, closed at one end but having a longitudinal opening as at 3 of a diameter of approximately one-half an inch, the tube itself being approximately an inch and one quarter in diameter. In the modification shown in Fig. 5 the active portion is spherical as at 4 and has a substantially spherical opening 5 therein. A rubber tube 6 is formed integral with the sphere 4 and the opening in the tube communicates with the chamber 5.

hen using either one of the rubber sound detectors shown in Figs. 4 and 5, a sound conveying tube is inserted in the open end of the detector and then the parts are clamped tightly together to make a watertight joint. Fig. 1 shows an arrangement of this character. In the arrangement there shown two of the devices 1, such as shown in section in Fig. 4, are mounted so as to be carried respectively at the ends of a horizontal rod or pipe supported so as to be rotated about a vertical axis. This horizontal member consists of metal pipes 7 and 8, screwed into a pipe fitting 9 and extending in opposite directions. A vertical pipe 10 is screwed into the upper member of the pipe fitting 9, and serves as a support for the pipes 7 and 8 and the parts carried thereby, and serves also as a means for rotating the pipes 7 and 8 about the vertical axis of the pipe 10. The rubber diaphragms 1 are supported respectively from the pipes 7 and 8 by means of clamps 11 and 12 fastened to brass sound conveying pipes 13 and 1-1, upon the ends of which the tubular diaphragms 1 have been applied and to which they have been clamped in a water-tight manner by means of clamps prevent access of water to the interior of the tube 10. For this purpose a species of stuffing-box with sound-insulating gaskets is indicated at 18. The pipes 13 and 14 where they pass through-the supporting member or pipe 10 are sound-insulated from the "latter in any suitable manner as by wrappings, such as 19, of wool, cotton or the like. The ends of the tube 7 and 8 are closed by caps 20 and 21 for preventing access of water to the interior.

v There the pipes 13 and 14 pro ect from the top of the apparatus connection is made to soft rubber tubesf22 and 2-3 leadlng to ear pieces 24 and 25 for the use of the observer. The total lengths of the air passages to the two car pieces should be equal.

In the practical operation of the apparatus the vertical member 10 and the parts supported therefrom are mounted so as to be easily rotated. If utilized ,on shipboard the dimensions of the parts are such that the sound-receiving diaphragms are pesitioned well below the level of the ships keel. In the particular arrangement shown in Fig. 1 the support is made through gimbals, some of the parts of which are shown somewhat more in detail in Fig. 3. Referring to both Fig. 1 and Fig. 3, a

flanged member 26 is fastened to the rod- 10 and is provided with an adjustable scale 27 graduated in degrees, as indicated, and fastened in place .by a clamping r ng 28. This flange rests upon a ring 29 which is pivoted to the ring 30 forming one member of the gimbal 31, the pivots being formed by the bolts 32. This same ring 30 is also pivoted at diametrically opposite points, as at 33, to a fixed frame 34. Assuming the device as a whole is to be used on shipboard, this frame 34 is carried on the end of a boom or rod 35 so as to space the device out from the side of the vessel. Sound insulation for the in-board end of the boomis provided to avoid the transmission of sounds from the ship through the rod. Suitable guys or sta s, or other supporting means,incomplete y shown, may be used for holding the parts in position.

Fi 2 shows a modified form of cross mem er in which hollow spheres 4, shown more in' detail in Fig. 5, 'are used in place of tubes 1. In this case the hollow spheres are as'before slipped over the ends of soundtransmitting tubes but in thiscase the tubes pass through the interior of the arms 36 and 37 instead of being supported exteriorly thereon. As before, these tubes are sound insulated from the protecting and carrying members 36 and 37 as well as from the upright tube, such as 38, but otherwise the apparatus may be the same as in Fig. 1. As in Fig. 1, theconstruction of the parts in Fig. 2 is such as to exclude water from the interior of the pipes and other parts.

In using the apparatus above described as a directional sound detector the operator applies the listening tubes 24 and 25 to his ears and listens. When a sound is heard, the direction of origin of which it is desired to know, the hand wheel 17 is turned, as will be explained ,so as to rotate the sound detectors 1, for. example, about the axis of the tube 10. The sound will then seem to the observer to come either from the right or the left and to shift from side to. side as the sound detectors 1 are shifted from side to side of a osition in which a line connecting the soun detectors is normal to the direc tion of the source of sound. After repeated trials the operator is able to find a position of the hand wheel 17 at which the sound appears to come from directly ahead. A reading of the dial 27 gives a measure-of this direction. o

It is to be observed however that the angle thus obtained is that of a line passing through the sound source and the point of observation While the location of the sound source may be in either one of the two opposite directions of the extension of that line. An error of 180 in direction is thus possible. Which of op osite directions is the correct one may be 'etermined by other cir cumstances, as by independent observations of like character made with similar apparatus from another point or'points, whereby the exact location ofthe sound source may be obtained by plotting the'intersection of direction lines so obtained.

A method of setting'the cross-bar 7, 8 carrying the sound receivin or detecting. devices so as to avoid Ima ing a directional error of 180 is as follows: If upon commencing the observation, the sound under observation appears to come, for example, from the right, then the operator causes the cross-bar to be rotated about its vertical axis toward what appears to be the direction of the sound, which in this case is to the right or in other words in the direction of rotation of the hands of a clock; and this rotation is continued, even if a turn through a full half circle is necessary, until the direction of sound appears to shift to the left. Thebar is then rotated in the reverse direction until the sound appears to shift to such a way sound appears to come from directly ahead. If the scale 27 has been adjusted originally so as to read zero when the cross-bar 7 and 8 faces in the direction of the ships .head-' ing, thenthe reading of the scale after the setting of the bar has been accomplished as above indicated, shows the bearin of the object in degrees relative to the ore-andaft line of the ship. It. will be evident that the ear pieces 24, 25 connected respectively to the sound receiving devices 1, 1, located on what may be considered the left and right hand arms of the bar 7, 8, are applied to the left and right -earsrespectively of the operator.

The ability for detecting the direction or line along, which sound proceeds by means of apparatus of the nature described, depends upon a remarkable ca ability which the human brain possesses or comparing the sound sensations received at the two ears. If the sound reaching one ear is obliged to pass through a greater distance in proceeding from the source of sound than does the corresponding sound wave reaching the other ear, then the sound producing ob ect appears to be, not directly in front of the observer, but at that side which is connected to the sound receiving device nearest the source of sound If both sound receiving devices are at equal distances from the source of sound, then the impression received b the observer is that the sound is straig t ahead. This capab1l1ty of the human ears is fre uentlyreferred to as the binaural sense. ile various theories have been advanced to ex lam the operation of this binaural sense, t e matter is one which is still only imperfectly understood. It had been supposed, for example, that the differential effect on the ears of the observer whereby he was able to locate a sound as coming either from one side or the other was due entirely to the difference in phase at which the sound arrived in the two cars. But this explanation is not satisfactory inthe case of a relatively pure .tone such as that from a flute orpenny whistle. The direction of sounds thus produced seems to bevdifiicult of determination through the exercise of the binaural sense. If, however, the sound to'be listened to is irregular in its nature, having what might be called salient characteristics, as for example a recurrent noise such as the beating of a ships engine or propeller or the clanging of the auxiliaries of a ships motive power apparatus, then the human ear and brain seem to be able to pick out'and comparet hese outstanding qualities inthe sound waves in as to receive a sense of direction of the sound source. Since the binaural sense seems thus to depend largely upon various salient characteristics of the'sound waves to be-examined,

it is important then that these sound waves .produced by the object, the location of which it is desired to find, should be transmitted to the ears of the observer in a condition as free as'possible from distortion or undue amplification of the component parts of the wave; so that each ear may .hear exactly the same quality of sound asthe other. I obtain remarkably satisfactory results by making the sound receiving devices such as 1, of soft Para rubber. Diaphragms of this material, perhaps because they are ractically free from resonance efare thus aperiodic, transmit to fects an the sound conveying tubes such as 13 and 14 to which they are connected, a true and faithful reproduction of the sound passing in the water. Itis to the use of soft rubher, or of material possessing the characteristics of rubber in the respects indicated,

forth the markedly successful utilization of would get a false impression as to the apparent direction from which the sound was proceeding in the water. Rubber also possesses the advantage that it is of ap roximately the same density as water an possibly for this reason among others, it is a good sound transmitter.

In actual practice the sound detecting devices should be located on their supporting arms at some considerable distance apart and e ually spaced from the vertical axis from w ich they are rotated. Within limits the reater the len th of radius of the device from the axis the greater is the accuracy with which the direction of sound may be determined. In a device havlng, for example, a distance of, say, four feet spread between the two sound receiving devices, that is to say, a radius of two feet, the direction of a line passing'from the sound source to the observer may be expected to be determined with an error of less than five degrees.

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. In a sound detecting device for subaqueous use, an unstretched and unstrained diaphragm of soft rubber.

2. Ina sound detecting device for subaqueous use, a substantially aperiodic diaphragm of soft rubber and a sound conveymg tube connected therewith.

3. A sound detecting device for submarine or subaqucous use having a sound 85 that I attribute by the means herein set receiving member consisting of an -un-" stretched or unstrained diaphragm having the qualities of soft rubber.

4. A binaural sound locating device for subaqueous sound detection having a plurality of sound detecting devices. spaced apart and having substantial aperiodic sound receiving and transmitting diaphragms of soft rubber.

5. A binaur'al sound locating .device having substantially aperiodic sound receiving members of rubber.

6. A sound receiving device for subaqueous use'having a substantially aperiodic sound receiving member of soft rubber.

7. In a sound receiving device for subaqueous use, a substantially aperiodic rubber sound receiving member,- and means for making perceptible the vibrations of said rubber sound receiving member caused by the reception of sound waves.

8. A binaural sound locating device com= prising a plurality of sound detectors having sound receiving members of a material having theessential characteristics of rubber, means for receiving at a distant point sound waves corresponding to those impressed upon said sound detectors, said means comprising sound receiversfor the respective ears of the observer, and means of sound detecting devices spaced apart and having sound receiving and transmitting diaphragms of, soft rubber and a sound conveying tube connected to each of said diaphragms, said sound conveying tubes.being of substantially .equal length and having ear pieces at the ends thereof.

13. In a sound detecting device for detecting sounds conveyed through a liquid medium, a substantially aperiodic diaphragm of soft rubber.

14,111 a sound detectin device for detecting sounds conveyed trough a liquid medium, a substantially aperiodic dia-' phragm having the qualities ofsoft rubber.

15. A binaural sound locating device for detecting sounds conveyedthrough a liquid medium, having a. plurality of sound refor adjusting at will the phase relation of the soundreceived at one ear. of the ob-- server relatively to .the' corresponding sound received at the other ear of the ob server. 9. A sound detecting device for subaqueous use having a substantially aperiodic diaphragm of elastic material hay ng approximately the same density as water.

10; A binaural sound locating device hav-, ing sound receiving members of soft rubberadapted to be submerged in water, and

means for conveying to the ears of an observer thevibrations of said 'rubber'sound receivin member cause'd by the reception of soun ,waves' in the water;

f-A binaural sound locating device hav v vibration detector ceiving devices spaced apart andhaving substantial] aperiodic sound'receiving' diaphragms 0 soft rubber.

16. A device for locating underwater vibrations comprising a rotatable shaft-one end of whichis arranged to be submerged,

a transverse arm-"secured to the submerged end of said shaft,- a detector including an I inherently damped vibration responsive element. of material having the qualities of soft rubber mounted on each end of said arm, tubes extending-from each detector to separate earpieces, and .means to rotate said shaft-f I a 17. Int binaural sound locating deviee, a

comprising an unstretched and self dampe'd diaphragm of a material having the ualities 0 soft rubber. In witness whereo I' have hereunto set my haiulgthis- 30th da] of September,"19l8.

WILLIA D. COOLI DGE. 

